The predicted role of steric specificity in crowding-mediated effects on reversible biomolecular association.

A fundamental question in biology is whether the presence of non-reacting macromolecules in the cytoplasm affects the rates and extents of reversible association reactions, a phenomenon often referred to as 'macromolecular crowding.' Under certain conditions, crowding has been proposed to dramatically alter the kinetics and thermodynamics of chemical reactions, making it difficult to quantitatively relate rates and extents of reactions measured in vitro to those occurring in vivo. In this work, we use Brownian dynamics simulation and Monte Carlo methods to (1) quantify the overall thermodynamic and kinetic effects of crowding by independently investigating each step of reversible bimolecular association (i.e. translational diffusion, steric specific binding, and dissociation), and (2) provide an explicit, quantitative investigation of how the degree of steric specificity of protein dimerization influences crowding-mediated effects on association and dissociation. We find that k on decreases by ∼2-fold for non-steric specific reactions, and increases by ∼3-fold for highly steric specific reactions. In addition, k off decreases by only ∼30%-60% in the presence of crowders, depending on the strength of the bond between the reactant pair, so that the equilibrium constant is increased by ∼4-fold, at most. These results suggest that crowding-mediated effects on globular protein dimerization reactions in the cytoplasm are modulated by the steric specificity of the reactants, and that reversible protein-protein association is relatively insensitive to the physical presence of crowders (i.e. steric repulsion effects in the cytoplasm) for crowders of similar size and shape to reactants over a range of volume fractions (0-0.3).

Comparison of topical anesthetics without cocaine to tetracaine-adrenaline-cocaine and lidocaine infiltration during repair of lacerations: bupivacaine-norepinephrine is an effective new topical anesthetic agent.

OBJECTIVE: To compare the effectiveness of four topical anesthetics that do not contain cocaine with that of topical tetracaine-addrenaline-cocaine (TAC) and lidocaine infiltration during laceration repair in children. DESIGN: This was a randomized, blinded trial. SETTING: The study was conducted in the emergency department of a large children's hospital. PARTICIPANTS: Subjects were children 2 years of age or older with a laceration 5 cm or less in length that required sururing. INTERVENTIONS: Patients were randomly assigned to receive one of four noncocaine-containing topical anesthetics, topical TAC, or lidocaine infiltration anesthesia before laceration repair. OUTCOME MEASURES: Outcome measures assessed pain perceptions using a Visual Analogue Scale, Likert scale, and Anethetic Effectiveness scale. Distress behaviors of patients were measured with the Restrained Infants and Children Distress Rating Scale. RESULTS: Two hundred forty patients were enrolled in the study. Using alpha = 0.05 and beta = 0.2, there was statistical power to detect differences of 0.3 to 1.3 U for the outcome measures used. The bupivacaine-norepinephrine topical solution (Bupivanor) performed better than the other three new topical preparations. It provided effective wound anesthesia during lacertion repair, especially for lacerations of the face and scalp, where it was consistently rated as effective as TAC and 1% lidocaine infiltration by all observer groups for all outcome measures. There was a 4% overall wound complication, including one wound infection. CONCLUSION: Bupivanor is an effective alternative to TAC and lidocaine infiltration for local anesthesia during laceration repair, expecially on the face and scalp. The effectiveness of Bupivanor on the face is important, because it is here where TAC is most likely inadvertently to come into contact with mucous membranes and result in systemic toxicity. Because pain and distress scores did not take into consideration the pain associated with the initial injection of lidocaine, the findings of this study conservatively estimate Bupivanor's effectiveness, compared with lidocaine infiltration.

Statistical considerations in pharmacokinetic study design.

Pharmacokinetic studies may generally be categorised into 3 types: (a) population-based investigations, (b) individual-based compartmental, or (c) individual-based noncompartmental research projects. Each type of study has advantages and limitations. Population-based investigations pool drug concentrations across more than 1 individual subject. From these data, estimates of pharmacokinetic parameters are calculated. NONMEM is the only computer program available to evaluate this type of information. Recently a method has been proposed which derives individual estimates from the information available from NONMEM. By combining these 2 procedures it is possible for the clinician to review and adjust the dosage regimen if necessary. Population-based studies require fewer design criteria than other methods and are adaptable to the clinical setting, i.e. subjects can be patients currently being treated with the drug under consideration. One distinct advantage to this type of study is the flexibility of sampling times and the capability of the clinician to use information from the critically ill, the geriatric patient or the very young child. These subjects would not be available for the individual-based type of study because of the relatively large number of samples needed. Individual-based pharmacokinetic studies can be divided into 2 types with respect to their evaluation: (a) compartmental and (b) noncompartmental investigations. The latter type of study was originally thought to require fewer assumptions than the former but subsequently it has been shown that noncompartmental analyses are more restrictive and are basically compartmental in their approach. These studies estimate parameters which the compartmental investigation does not usually consider. These include area under the moment curve (AUMC) and mean residence time (MRT).(ABSTRACT TRUNCATED AT 250 WORDS)

Further improvement of the enzyme-linked antiglobulin test (ELAT) for erythrocyte antibodies.

The enzyme-linked antiglobulin test (ELAT) was found to be nine times more sensitive than the direct antiglobulin test (DAT) in detecting erythrocytes sensitized by IgG antibody in vitro. The release of hemoglobin and other interfering substances from the erythrocytes gave falsely high absorbance values which were corrected by the use of a hemolysis bland with each test. ELAT results showed good precision. With the use of the hemolysis blank, the ELAT should prove to be a useful tool for hospital blood blanks in the detection of weakly reactive allo- and autoantibodies.

Population requirements for capitation planning in pediatric cardiac surgery.

OBJECTIVE: To determine the population number necessary to generate a sufficient volume of pediatric cardiac surgeries to allow accurate prediction of resource utilization. DESIGN: All pediatric cardiac surgical patients receive care in our institution by means of only four clinical pathways that are based on acuity, not diagnosis or procedure. This allows accurate tracking of resource utilization. Based on available information, 750 consecutive surgically treated patients were retrospectively assigned to a pathway. They were subsequently subdivided into study groups of decreasing sizes from 150 to 35. Variability of pathway distribution from group to group was examined as a measure of the ability to predict resource utilization based on group size. Pediatric cardiac statistics from the state of Ohio were then used to extrapolate to the population base necessary to generate each group size. SETTING: A regional pediatric cardiac referral center. PATIENTS: All sequential patients who underwent pediatric cardiac surgery between July 1991 and January 1994. RESULTS: Statewide statistics showed that a population base of 1 million people generates 100 pediatric cardiac operations. Groups of 100 patients or greater had minimal variation in pathway distribution from group to group, allowing accurate prediction of hospital charges. This was not true for groups of 50 patients or less. CONCLUSIONS: Resource utilization for pediatric cardiac surgery can be accurately predicted in a capitated setting for populations of 1 million covered lives (100 procedures) or greater. For populations of 500 000 covered lives or less, variability of case mix is great enough to suggest the need for a more individualized payment mechanism.

Clinical pathways can be based on acuity, not diagnosis.

The standardization of medical practice is gaining acceptance as a technique for controlling length of stay and hospital charges, while maintaining quality. Most clinical pathways address specific diagnoses or procedures, but we have developed a new approach in which pathways for cardiac care are based on acuity. All congenital cardiac surgical care rendered at Columbus Children's Hospital now falls within one of four such clinical pathways. This simplified approach is easy to use and has been well accepted. Our experience in a group of 107 consecutive patients treated in this fashion is described. The results of variance analyses, along with length of stay and charge data, are presented to demonstrate the degree to which resource utilization can be standardized in this widely variable group of patients whose problems were made cohesive by classification according to acuity level. We conclude that the resultant standardization offers considerable advantages for the managed care environment.

Pharmacokinetics and dosage of oxytetracycline in dogs.

The pharmacokinetics of oxytetracycline, which was given as a single intravenous dose (5 mg/kg), was studied in normal beagle dogs. Renal function was evaluated by the single injection technique and based on clearance of the radioiodine compounds 125I-iothalamate and 131I-iodohippurate. Values of GFR (4.42+/-0.77 ml/kg/min) and ERPF (12.91+/-1.49 ml/kg/min) showed normal renal function. The disposition curve describing decline of oxytetracycline activity in serum was described mathematically by a triexponential expression. Body clearance was 4.23+/-1.29 ml/kg/min. A dosage regimen (intravenous route of drug administration), based on overall elimincation rate constant (0.1155 h-1) and apparent specific volume of distribution (2 litre/kg), and consisting of a priming dose (10 mg/kg) followed by maintenance doses (7.5 mg/kg) at 12 h intervals was proposed. This dosage regimen was predicted to rapidly achieve and maintain steady state serum concentrations within the range 1.25 to 5.0 microgram/ml, which is therapeutic level for the majority of susceptible microorganisms.

Ventricular wall thickness in the fetal dog.

Ventricular wall thickness of 21 50-to 60-day canine fetuses was determined by direct measurement with calipers. Measurements were made of the left and right ventricular walls and of the interventricular septum, perpendicular to the apico-basilar axis at the location just below the aortic valve, and midway between the coronary sulcus and the apex. Mean determiniations were used to characterize the wall thickne-s at the various levels. The right wall was found to be thickpreciable thickness differences between the septal and left wall at this location. At the level of the midventricular wall, the septal wall thickness exceeded that of the left and right wall. Left and right wall thickness at this level were similar.

Single- and repeat-dose pharmacokinetic studies of chloramphenicol in horses: values and limitations of pharmacokinetic studies in predicting dosage regimens.

A single-dose pharmacokinetic study of chloramphenicol in propylene glycol was done in 6 horses after 22 mg/kg was administered IV. Serum drug concentrations obtained at various predetermined intervals were determined by an electroncapture gas-chromatographic technique. The time-concentration data were described by a 2-compartment open model, and various pharmacokinetic variables were estimated. The median elimination rate constant was estimated to be -0.0185 minute-1 (-0.0225 to -0.0148 minute-1), and the median half-life was 37.36 minutes (30.74 to 46.90 minutes). The median apparent volume of distribution and total body clearance were 1.46 L/kg (1.13 to 1.60 L/kg) and 25.56 ml/kg/min (23.66 to 32.21 ml/kg/min), respectively. On the basis of these data, single- and repeat-dose kinetic studies were done in another group of 6 animals. The drug was administered at a dosage of 22 mg/kg every 4 hours for 3 days. Blood samples were obtained for pharmacokinetic studies after the first and the last doses were given. The half-life, volume of distribution, and total body clearance did not change significantly (Wilcoxon signed rank test) after 3 days of therapy with chloramphenicol. The IV dose schedule for treating bacterial infections with organisms of different sensitivities has been determined from the estimates of the pharmacokinetic variables. The limitations of calculating the dose schedules for chloramphenicol on the basis of pharmacokinetic variables in horses are discussed.

Trimethoprim and sulfadiazine: experimental infection of Beagles.

The purpose in the present study was to determine whether the commercial combination of trimethoprim (TMP) and sulfadiazine (SDZ) tribrissen (TRI) was more effective than either of the components for treating experimentally induced infection of Streptococcus zooepidemicus. Two dose levels of each were given subcutaneously for treatment, and their effectiveness was compared with that of sulfadimethoxine (SDM) in terms of (i) clinical manifestations, (ii) hematologic changes, (iii) blood culture examinations, and (iv) tissue culture examinations. According to these four measurements, the combination TMP/SDZ was more effective than either of the components. This effect was observed at the two dosages of TRI (30 and 15 mg/kg). The higher dosage, however, was more effective as demonstrated by three of the measurements. Alone, TMP and SDZ were not effective, but SDM treatment was effective in this model.

Relationship between serum and brain concentrations of phenytoin in the dog.

The concentrations of phenytoin (DPH) in the CNS of adult dogs given the drug by IV injection, continuous IV infusion, or repeated daily oral administration and of newborn pups given DPH by IV injection were consistently proportional to serum concentrations of the drug at the time of blood sample collections. Adult dogs injected IV with [14C]DPH failed to show predilection of the drug for the 13 anatomic brain sections sampled. The pharmacokinetics of DPH were studied in adult and neonatal dogs given 15 mg of the drug/kg of body weight as a single IV injection. The mean half-life of the drug in adult dogs injected IV was 4.5 hours. The serum half-life of injected DPH was lowest in pups 30 days of age when compared with that in other age groups. The serum half-life of injected DPH was increased in adult dogs under pentobarbital anesthesia.

Comparison of topical anesthetics with lidocaine infiltration during laceration repair in children.

This study is a randomized, blinded trial that compares the effectiveness of a new topical anesthetic preparation of 2% mepivacaine and 1:100,000 norepinephrine (Mepivanor); a topical solution of 1% tetracaine, 1:4,000 adrenaline, and 4% cocaine (TAC); and 1% lidocaine infiltration during laceration repair in children. The study was conducted in the emergency department of a large academic children's hospital. Study participants were children 2 years of age or older with a laceration on the face or scalp, 5 cm or less in length, that required suturing. Patients were randomly assigned to receive Mepivanor topical solution, TAC topical solution, or lidocaine infiltration anesthesia prior to laceration repair. Seventy-one patients were enrolled in the study during a 2-month period. Outcome measures assessed pain perceptions using a Visual Analogue Scale (VAS) and a seven-point Likert scale. There was statistical power to detect differences of 1.2 to 1.7 units for the VAS outcome measures using alpha = 0.05 and beta = 0.20. There were no statistically significant (P > 0.05) differences between TAC and 1% lidocaine infiltration in providing effective anesthesia. Mepivanor was generally less effective in providing adequate anesthesia during laceration repair than TAC and lidocaine infiltration, with Tukey's post hoc test for ANOVA demonstrating statistically significant (P < 0.05) differences between Mepivanor and these agents for research assistant and suture technician VAS scores. Wound blanching was judged to be less with Mepivanor than with TAC, although this difference was not statistically significant. There were no adverse reactions, wound infections, or healing difficulties for any of the patients who received TAC or Mepivanor. It was concluded that non-cocaine-containing Mepivanor was generally less effective than TAC and lidocaine infiltration in providing adequate local anesthesia during laceration repair. TAC containing only 120 mg of cocaine (3 mL of 4% cocaine) was as effective as 1% lidocaine infiltration in providing local anesthesia during laceration repair. This will allow the amount of cocaine in TAC to be reduced, thereby decreasing costs and the likelihood of adverse reactions.

Experimental Pseudomonas aeruginosa ulcerative keratitis model in the dog.

Primary Pseudomonas aeruginosa ulcerative keratitis and accompanying secondary ocular disease were induced bilaterally in 12 of 12 dogs subjected to corneal trephination and intrastromal inoculation. Successful experimental infection was based on recovery of viable Pseudomonas organisms from the lesions, as well as gross and biomicroscopic appearance of the corneas.

A pharmacokinetic analysis of tylosin in the normal dog.

Studies were conducted to determine certain kinetic variables for tylosin in the normal dog. These variables were determined by pharmacokinetic analysis, measuring the decrease in serum concentration of tylosin activity in 3 separate experiments. Tylosin, given as a single intravenous dose of 10 mg of tylosin activity/kg of body weight, was calculated to have an elimination half life (t1/2beta) of 54 minutes and was no longer detectable in the serum by assay methods at about 270 minutes. In addition, tylosin appeared to be highly distributed with an apparent volume of distribution of about 1.7 L/kg and a tissue-to-plasma ratio of about 0.7. The body clearance of tylosin was calculated to be about 22 ml/kg minute. A separate multiple-dose intravenous experiment with the same dose per injection was conducted and showed similar results. Also, single intramuscular injection of 10 mg of tylosin activity/kg showed tylosin to peak after injection in the serum at 30 minutes, attaining a concentration of approximately 1.5 mug/ml. This concentration was maintained through 60 minutes and decreased slowly through 540 minutes. Data generated through 17 clinical cases indicated that the minimum inhibitory concentration for tylosin in Pasteurella spp tested was about 6.25 mcs/ml and for hemolytic Staphylococcus spp tested greater than or equal to 0.4 mug/ml. Thus, it would appear that tylosin, given at the recommended dose (6.6 to 11.0 mg tylosin activity/kg of body weight once or twice per day), would produce serum levels insufficient to treat all Pasteurella spp and some hemolytic Staphylococcus spp tested since a serum level of tylosin at slightly higher than 1 mug/ml for about 30 minutes was achieved in this study.

Pedigree analysis of Abyssinian cats with familial amyloidosis.

Pedigrees of 62 Abyssinian cats with familial amyloidosis were compared with those of 100 Abyssinian cats registered with the Cat Fanciers Association. The inbreeding coefficients of the 2 samples of cats were not significantly different. Analysis of the pedigrees with respect to specific ancestors, however, showed that certain cats were significantly more common in the pedigrees of affected cats than in those of cats in the randomly selected sample. These data support a genetic basis for this disease, but do not allow determination of the mode of inheritance.

Tetracaine-lidocaine-phenylephrine topical anesthesia compared with lidocaine infiltration during repair of mucous membrane lacerations in children.

This study compared the effectiveness of a new topical anesthetic, tetracaine-lidocaine-phenylephrine (TetraLidoPhen), with that of lidocaine infiltration during repair of mucous membrane lacerations in children. It was conducted in the emergency department of an urban children's hospital with use of a prospective, randomized, blinded study design. Participants were 90 children 1 year of age or older with a laceration 5 cm or less in length on or near a mucous membrane that required suturing. They were randomly assigned to one of two treatment groups, with 45 patients in each group. Pain felt during suturing was scored by suture technicians, research assistants, a videotape reviewer, parents, and patients 5 years of age and older using a Visual Analogue Scale (VAS). Suture technicians, research assistants, a videotape reviewer, and parents also scored pain using a seven-point Likert scale. In addition, suture technicians completed an Anesthesia Effectiveness scale and a Wound Blanching scale. The laceration was located near the eyes in 71 patients (79%), and on or near the lips in 19 (21%). Lidocaine infiltration performed significantly better than topical TetraLidoPhen in comparisons of Likert scores of suture technicians (P = 0.007), research assistants (P = 0.005), the videotape reviewer (P = 0.003), and parents (P = 0.03); Anesthetic Effectiveness scale scores of suture technicians (P = 0.00002; relative risk (RR) = 1.83, 95% confidence interval 1.36 < RR < 2.46); and VAS scores of suture technicians (P = 0.002), research assistants (P = 0.001), and the videotape reviewer (P = 0.005). No significant difference in performance was detected between lidocaine and TetraLidoPhen in comparing VAS scores of parents and patients. There was a 4.4% wound complication rate, including two (2.2%) wound infections. The authors conclude that TetraLidoPhen is a new topical anesthetic that appears to be safe when applied on or near mucous membranes. Its performance among study participants was statistically inferior to that of lidocaine infiltration; however, the differences in pain scores were small and may not be clinically significant. Also, comparisons of pain scores in this study did not take into account the pain associated with the initial injection of lidocaine. Therefore, study findings may underestimate the comparative performance of TetraLidoPhen. Further investigation of this new topical anesthetic is warranted.

The lipid composition of milk from mice fed high or low fat diets.

Total fatty acids and the proportions of methyl esters of individual fatty acids were measured in mouse milk. Pregnant mice were fed either a high fat (HF) diet or a low fat (LF) diet from 14 days of gestation. After parturition, each dam was milked once a day for a period of 18 days. The mean total fatty acid concentration over the entire study period was 110 mg/g of milk (approximately 11.7% fat as triglyceride) for both dietary treatment groups. During days 2 to 6 postpartum, the mean total fatty acid concentration for dams fed HF diet was lower than for the LF group. Although the concentration of total fatty acids of mouse milk was not affected by the level of dietary fat fed to the dam, several variations in the proportions of individual fatty acids were observed.

Statistical considerations in clinical field evaluation of drugs.

Statistical problems associated with clinical field evaluation of drugs are many. The Food and Drug Administration requires that the safety and efficacy of a drug must be shown in adequate and well-controlled clinical investigations. From a statistical point of view, safety and efficacy must be precisely defined, and a quantitative method must be developed to measure these properties. It is proposed that efficacy be defined in both the therapeutic and pharmacologic aspects. Further, to measure therapeutic efficacy, it is suggested that an appropriate health index be used. This index would provide information regarding degree of improvement and also the time course of improvement. To measure or evaluate pharmacologic efficacy, it is suggested that kinetic studies be done to compare half-lives, volumes of distribution, and any other relevant kinetic parameter(s).

Seizure classification in dogs from a nonreferral-based population.

On initial evaluation for onset of seizure disorders at nonreferral veterinary practices, 50 previously healthy dogs were enrolled in a study to determine the probability of identifying a specific cause for the seizures. Treatment was not administered prior to entry of dogs in the study. On the basis of antemortem and postmortem test results, 22 dogs (44%) were classified as having primary epileptic seizures (PES; idiopathic or without identifiable cause), 23 (46%) had secondary epileptic seizures (SES; identifiable intracranial cause), and 5 (10%) had reactive epileptic seizures (RES; metabolic or transient noxious cause). Forty-one dogs (82%) had 2 or more seizures before evaluation, with 37 (90%) of these dogs classified as having epilepsy on the basis of an underlying chronic brain disorder. For these 41 dogs, 17 (41%) had PES, 20 (49%) had SES, and 4 (10%) had RES. Among the 9 dogs (18%) with nonrecurring seizures, 5 had PES, 3 had SES, and 1 had RES. Generalized seizures were the most common first-observed seizure type associated with all etiologic classifications in all dogs with recurring and nonrecurring seizures. Diagnosis of SES was statistically more probable when the dog was less than 1 or more than 7 years old at the first seizure, when the first seizure was a partial seizure, or when the first seizure occurred between midnight and 8 AM. A diagnosis of RES was statistically more probable only when the interval between the first and second seizure was brief (< or = 4 weeks).(ABSTRACT TRUNCATED AT 250 WORDS)